Publications

High-speed x-ray stereo digital image correlation for fluid-structure interactions in a shock tube

James, Jeremy W.; Jones, Elizabeth M.; Quintana, Enrico C.; Lynch, Kyle P.; Halls, Benjamin R.; Wagner, Justin W.

X-ray stereo digital image correlation (DIC) measurements were performed at 10 kHz on a jointed-structure in a shock tube at a shock Mach number of 1.42. The X-ray results were compared to optical DIC using visible light. In the X-ray measurements, an internal surface with a tantalum-epoxy DIC pattern was imaged, whereas the optical DIC imaged an external surface. The environment within the shock tube caused temperature and density gradients in the gas through which the structure was imaged, therefore leading to spatial and temporal index of refraction variations. These variations caused beam-steering effects that resulted in bias error in optical DIC measurements. X-rays were used to mitigate the effects of beam-steering caused by the shock tube environment. Beam displacements measured using X-ray DIC followed similar trends (slopes, oscillations amplitudes and frequencies) as optical DIC data while ignoring beam-steering effects. Power spectral densities of both measurements showed peaks at the natural frequencies of the structure. X-ray DIC also has the advantage of being able to image internal structural responses, whereas optical DIC is only capable of measurements on the outer surface of objects.